1. Field of the Invention
The present invention relates to a portable electronic apparatus, called an IC card, incorporating an IC (Integrated Circuit) chip having a nonvolatile memory and a control element such as a CPU and, more particularly, to an area access method of the memory
2. Description of the Related Art
Recently, a so-called IC card incorporating an IC chip having an erasable nonvolatile memory and a control element such as a CPU has been developed as a new portable data storage medium. A plurality of identification (ID) numbers are registered in an IC card of this type. The IC card has a means for permitting an access to its internal memory only when a collating result between an externally input ID number and a registered ID number is affirmative. Thus, the IC card is considered as a data storage medium having high secrecy.
In use, a memory is divided into a plurality of areas so as to cope with a variety of applications. Each area is logically accessed as an object to be accessed. Therefore, since a physical data storage position of the memory cannot be externally known, high secrecy can be assured. Since an access is logically made, external memory management can be facilitated.
An IC card having a memory which is divided into a plurality of areas is disclosed in U.S. Pat. No. 4,734,568, for example.
Each area of the memory has inherent ID data, called an area number. When the ID data is designated in instruction data, the IC card identifies a destination of area access, and recognizes a physical storage position to access the area.
Recently, multi-purpose IC cards have also been developed. For example, a single IC card may be utilized as a cash card for a bank, a credit card, a leisure card, an electronic memorandum card, and the like. For example, when a single IC card is utilized as a cash card for a bank and a credit card, since a holder of the cash card and the credit card is the same person, it is preferable that a holder's name, address, telephone number, and the like are commonly stored so as to effectively use a memory area. Thus, the common holder can be accessed when either the cash or credit card is used. When a given area in the IC card is used as a bankbook, the IC card must be arranged so that the given area can be accessed by a bank but cannot be accessed by a credit card company for the purpose of keeping secrecy.
When a holder's name of the cash card and a holder's name of the credit card are registered in different areas, a problem may be posed in updating processing of a holder. For example, assume that when a woman changes her surname upon marriage, she updates a holder's name of the cash card but does not update a holder's name of the credit card. This causes a problem in use of an IC card. From this point of view, a single holder's name common to the cash card and the credit card is preferably registered in a specific area of an IC card. In other words, the IC card preferably has a common data field which can be accessed regardless of applications, and an application data field in which an area corresponding to a given application can be accessed and cannot be accessed in other applications.
However, in a conventional IC card, areas physically arranged on a memory have area numbers in one-to-one correspondence. For this reason, it is impossible to access an identical area using different area numbers or to access an identical area in different applications.